Brushless DC motor and manufacturing method thereof

ABSTRACT

A brushless DC motor includes an embedded memory of a micro computer mounted on a circuit board which can be modified during and/or after a manufacturing process of the brushless DC motor. The circuit board installed on the brushless DC motor includes an IC having the embedded micro computer executing feed back control of the pulse wide modulation and the embedded memory for storing data such as control programs. The circuit board also includes a writing terminal port to which an external memory writer is to be connected. Data is transferred from the external memory writer and stored in the embedded memory by contacting the writing terminal port with a tip end portion of a cable from the external memory writer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a brushless DC motor, andmore particularly relates to a brushless DC motor which includes arotation-control portion for controlling the rotation of the motor basedon data stored in memory and a driving circuit for providing drivingcurrent controlled by the rotation-control portion.

2. Description of the Related Art

Brushless DC motors are used for various applications such as officeelectronics, home electronics, and car electronics. In someapplications, the rotation of such brushless DC motors needs to becontrolled with great accuracy.

The rotation-control portion of the brushless DC motor may be equippedwith an IC having an integrated micro computer. Generally, the microcomputers have embedded memories, and the micro computer used for therotation-control portion includes a control program which regulates thedriving current supplied to a stator based on a rotational state of themotor, temperature, and external signals. The rotation of the motorincluding such a rotation-control portion can be more sophisticatedlycontrolled compared to motors without such control portions.

Conventionally, a read-only nonvolatile memory (ROM) is used for theembedded memory of the micro computer. The control program such as afeedback control program is stored in the ROM of the micro computer.Then, the micro computer with the ROM is mounted on a circuit boardwhich is to be installed onto the brushless DC motor.

The rotational setting of such a brushless DC motor can be variouslymodified by modifying the control program installed in the ROM.

Generally, two kinds of memories are used for the embedded memories ofthe micro computers; a one time programmable read only memory (anOTP-ROM) and an electrically erasable programmable ROM (an EEP-ROM or aflash memory). The OTP-ROM is inexpensive compared to the flash memory,therefore the micro computer with the OTP-ROM (OTP micro computer) isgenerally used for products in mass-production. However, when the designor configuration of the product is changed, the OTP micro computer onthe motor needs to be replaced because the program stored on the OTP-ROMcannot be modified. If the micro computer has been already mounted onthe circuit board, or the circuit board with the micro computer has beenalready installed onto the motor, replacing the micro computer will be aburdensome and time-consuming task, which greatly affects the efficiencyof manufacturing the motor. Moreover, the replaced OTP micro computerneeds to be discarded or stored so as to reuse them for other productmodels, which makes the efficiency of manufacturing the motor even less.The OTP micro computer is inexpensive itself, but as a result of theburdensome and time-consuming task mentioned above, the conventionalbrushless DC motor with the OTP micro computer is expensive and requiresmore time for its production.

In designing the control portion of the motor, ROM data of the motor isfrequently required, and the brushless DC motor equipped with the microcomputer in which access to the embedded memory of the micro computerduring or after the manufacturing thereof is in demand. However, thecircuit board is generally attached to the inside of the brushless DCmotor, and it is generally inaccessible from outside of the motor.

SUMMARY OF THE INENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a brushless DC motor in which anembedded memory of a micro computer mounted on the circuit board can bemodified during and/or after the manufacturing process.

According to one preferred embodiment of the present invention, abrushless DC motor includes a rotor portion rotatable about a centeraxis and including a magnet, a stationary portion including an armaturefacing the magnet and formed by winding a wire around a stator core, abearing rotatably supporting the rotor portion relative to thestationary portion, a circuit board connected to and facing thearmature, a rotation control portion provided on the circuit board andincluding a non-volatile rewritable memory for controlling the rotationof the rotor portion based on data stored on the non-volatile rewritablememory, a driving circuit provided on the circuit board for providingdriving current controlled by the rotation-control portion, and awriting terminal port provided on the circuit board to which an externalmemory writer is detachably connected.

According to another preferred embodiment of the present invention, themotor further includes an impeller arranged on the rotor portion; abearing housing having a hollow cylindrical shape, an inside of whichsupports the bearing and an outside of which supports the armature; abase portion extending radially outwardly from the bearing housing; ahousing surrounding the impeller and defining a passage of air flow; anda supporting arm supporting the base portion relative to the housing byconnecting the housing and the base portion. The circuit board isarranged axially between the armature and the base portion.

According to another preferred embodiment of the present invention, thewriting terminal port is arranged on a base-portion-side surface of thecircuit board facing the base portion, the base portion includes awriting opening, and the external memory writer is detachably connectedto the writing terminal port via the writing opening. By virtue of thisconfiguration, the settings or design of the motor may be modifiedwithout replacing the already installed circuit board.

Generally, a portion of the circuit board is exposed by detaching therotor portion of the motor. Therefore, the circuit of the motor isgenerally accessible from the rotor side (the armature side) of thecircuit board. In another preferred embodiment of the present invention,the writing terminal port is arranged on the armature side of thecircuit board, and the writing terminal port is accessible from thearmature side of the circuit board even if it is not accessible from thebase side of the circuit board, which makes it possible to write data inthe memory after and/or during the manufacturing of the motor. Inaddition, settings of the motor are easily modified after manufacturingthe motor without changing the hardware configuration. Therefore, it isnot necessary to discard or store the replaced circuit board and/orelectric components such as micro computers to reuse them, and it makesmanufacturing of the motor more efficient.

According to another preferred embodiment of the present invention, acircuit board of the motor may include a protruding portion whichprotrudes from a base portion of the motor, and the writing terminalport may be arranged on the protruding portion. According to anotherpreferred embodiment of the present invention, a circuit board of themotor may include a writing terminal port on its side surface. Accordingto another preferred embodiment of the present invention, an externalwriting terminal port which is connected to the writing terminal port byan auxiliary cable is provided.

By virtue of the configurations mentioned above, the writing terminalport arranged on the circuit board is easily accessible during and/orafter manufacturing of the motor. Therefore, the data stored in thememory is easily modified, and data such as rotational settings of thefan can be modified without changing the hardware configuration. Inaddition, it is not necessary to discard or store the replaced circuitboard and/or electric components such as micro computers to reuse them,and it makes manufacturing of the fan more efficient.

A method of manufacturing the fan equipped with the motor is alsoprovided. According to preferred embodiments of the present invention,the manufacturing method includes a data-writing step in whichpredetermined data is written in the memory of the fan by connecting thecircuit board and a cable connected to an external memory writer. In thedata-writing step, a tip end of the cable is contacted to the writingterminal port from an armature side of the circuit board.

Moreover, the data-writing step may be performed after connecting thecircuit board and the armature then fixing the armature to the baseportion. Furthermore, the manufacturing method may further include aninspection step in which the rotation of the fan is inspected, adetaching step in which a rotor portion is detached, and thedata-writing step. The rotor portion of the fan identified as a defectfan during the inspection step is detached and the data-writing step isperformed again.

Other features, elements, steps, processes, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an axial fan according to a firstpreferred embodiment of the present invention.

FIG. 2 is a cross sectional view of the axial fan shown in FIG. 1.

FIG. 3 is a plan view of a circuit board installed onto the axial fan.

FIG. 4 is a plan view of the axial fan according to a second preferredembodiment of the present invention in the state that an impellerassembly thereof is detached.

FIG. 5 shows a probe (a connector of a control cable) which is a portionof an external device for writing data in an embedded memory of a microcomputer mounted on the axial fan.

FIG. 6 shows a cross sectional view of the axial fan according to amodified preferred embodiment of the present invention.

FIG. 7 shows a cross sectional view of the axial fan according toanother modified preferred embodiment of the present invention.

FIG. 8 shows a cross sectional view of the axial fan according toanother modified preferred embodiment of the present invention.

FIG. 9 shows a cross sectional view of the axial fan according toanother modified preferred embodiment of the present invention.

FIG. 10 shows a cross sectional view of the axial fan according toanother modified preferred embodiment of the present invention.

FIG. 11 is a plan view of a circuit board installed to the axial fanaccording to a third preferred embodiment of the present invention.

FIG. 12 shows a cross sectional view of the axial fan in the state thatthe impeller assembly thereof is detached.

FIG. 13 is a flow chart illustrating a manufacturing method of the axialfan according to a preferred embodiment of the present invention.

FIG. 14 is a flow chart illustrating a manufacturing method of the axialfan according to a preferred embodiment of the present invention.

FIG. 15 shows a perspective view of the axial fan according to amodification of the second preferred embodiment of the presentinvention.

FIG. 16 shows a perspective view of the axial fan according to amodification of the second preferred embodiment of the presentinvention.

FIG. 17 is a perspective view of an axial fan according to a fourthpreferred embodiment of the present invention.

FIG. 18 is a block diagram of the relationship between the circuitboard, driving circuit, micro-computer integrated circuit, writingterminal port, probe, and external memory writer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 17, preferred embodiments of the presentinvention will be described in detail, in which a brushless DC motor isused as a motor of an axial fan for cooling a computer. In the followingdescription, an axial direction indicates a longitudinal direction of arotation axis, and a radial direction indicates a directionperpendicular to the center axis of the rotation of the brushless DCmotor.

First Preferred Embodiment

Referring to FIGS. 1 to 3, the first preferred embodiment of the presentinvention will be described below.

An axial fan 1 shown in FIG. 1 includes a motor (brushless DC motor), animpeller 4 attached to the motor, and a housing 2 supporting the motorand arranged so as to radially surround the impeller 4. The housing 2 isdefined by a hollow cylindrical body 3, an upper flange portion 30, abottom flange portion 35, a base portion 80, and a plurality ofsupporting arms 9 which are integrally formed into a single memberpreferably made of synthetic resin, for example. The hollow cylindricalbody 3 radially surrounds the impeller 4. The upper flange portion 30 isarranged radially outside of an upper opening of the hollow cylindricalbody, and the bottom flange portion 35 is arranged radially outside of abottom opening. The base portion 80 supports the motor and the impeller4 at an inside of the hollow cylindrical body 3. The plurality ofsupporting arms 9 radially extend from the base portion 80 to the hollowcylindrical body 3 so as to support the base portion 80. A space betweenthe cylindrical body 3 and base portion 80 defines a passage for airflow. The air is taken from one end opening and is exhausted to theoutside of the housing 2 through the space. The base portion 80 includesan outer circumferential wall axially extending toward impeller 4whereby the base portion 80 is formed into a cup shape.

As shown in FIG. 2, the impeller 4 includes a cup-shaped motor case 6and a plurality of blades 7 arranged at an outer circumferential surfaceof the motor case 6. A motor body 5 is inserted into the motor case 6 sothat the motor case 6 is attached to a rotor portion of the motor. Acylindrical bearing housing 85 is arranged at a middle portion of thebase portion 80. A pair of bearings is fixed within the bearing housing85, and an armature 10 is fixed to the outside of the bearing housing85. The pair of bearings rotationally support a rotational shaft 5 aarranged in the middle portion of the impeller 4 whereby the impeller 4is rotatably supported. A magnet 68 is fixed to the inside of the motorcase 6 via a yoke 65 so that the magnet 68 faces the armature 10. Thearmature 10 includes a stator core formed by laminating Si-Steel plates.An insulating layer is provided on the stator core and a wire is woundaround a portion of the stator core to form a coil thereon. In the motoraccording to this preferred embodiment of the present invention, astationary portion of the motor is defined by the bearing housing 85 andthe base portion 80, and the rotor portion is defined by the yoke 65 andthe rotational shaft 5 a.

A control portion of the motor body 5 includes a rewritable non-volatilememory (flash memory) 122, a rotation-control portion 121 forcontrolling the rotation of the motor based on he data stored in thememory, and a driving circuit 123 for providing driving currentcontrolled by the rotation-control portion (each shown in FIG. 18). Thecontrol portion is configured so as to the execute feedback control ofthe pulse width modulation (PWM) by using a microcomputer. To executethe feedback control, the circuit board 110 includes a micro-computerintegrated circuit 12 (hereinafter simply referred to as IC 12) havingan embedded micro computer, an embedded memory, such as the rewritablenon-volatile memory 122, storing data, and a program for the feedbackcontrol that defines the rotation-control portion 121.

As shown in FIG. 3, the circuit board 110 is in a substantially annularshape having a center opening to which the bearing housing 85 of thebase portion 80 in inserted. An outer diameter of the circuit board 110is substantially the same as an internal diameter of the outercircumferential wall of the base portion 80. A circuit pattern isprinted on both sides of the circuit board 110, and electroniccomponents including the IC 12 are mounted on one side 111 of thecircuit board 110, wherein the one side 111 is facing toward the baseportion 80. FIG. 3 shows a portion of the circuit pattern and thecomponents. The circuit board 110 is fixed to the armature 10 bysoldering a plurality of connection pins provided on an insulator of thearmature 10 to the circuit board 110. The coil is connected to theconnection pins whereby the coil and the circuit board 110 areelectrically connected via the connection pins.

An external connection port 13 including a plurality of terminal pins131 is arranged at an outer circumferential portion of a base portionside 111 of the circuit board 110. One end of a cable M is soldered tothe external connection port 13, and another end of which is connectedto external power supply and/or the external control circuit. As shownin FIG. 1, the base portion 80 includes a wiring opening 14 and a guidegroove arranged on one of the supporting arms 9, through which the cableM connected to terminal pins 131 is led outside of the housing 2.

As shown in FIG. 2, the circuit board 110 is accommodated in thesubstantially cup-shaped base portion 80 and includes the controlportion having IC 12 on one side 111 thereof which faces the baseportion 80. Also on side 111 of the circuit board which faces the baseportion 80, a writing terminal port 150 to write data in the embeddedmemory of the IC 12 is provided.

In this preferred embodiment of the present invention, the writingterminal port 150 is preferably defined by five terminal pins 151, whichare connected to the embedded memory through circuit patterns (not shownin the drawings). By connecting the writing terminal port 150 and anexternal memory writer 164 (shown in FIG. 18) with a control cable, itbecomes possible to write data to the embedded memory.

The procedure to modify data stored in the embedded memory of the IC 12installed onto the axial fan 1 is described below. First, power supplyfor the axial fan 1 is shut off. Second, a probe 160, which is arrangedon the tip end of the control cable extending from the external memorywriter, is inserted into the wiring opening 14, and then the tip end ofthe probe 160 is connected to the write terminal port 150 (see FIG. 5).Third, by activating the external program writer, data stored inembedded memory of the IC 12 may be modified. After modifying data inthe embedded memory, access to the memory is shut off to prevent thedata stored in the memory from leaking out or being altered. Forexample, the wiring opening (the writing opening) may be closed byattaching a name plate to the base portion 80. Alternatively, arectangular cap may be attached so as to close the wiring opening 14.

The writing terminal port 150 is arranged so as to face the wire opening14. Therefore, like the external connection port 13, the writingterminal port 150 is exposed to the outside of the axial fan 1 throughthe wire opening 14. In other words, in this preferred embodiment of thepresent invention, the wiring opening 14 is also used as a writingopening whereby it is not necessary to provide the writing openingseparately. By virtue of the configuration in which the opening area ofthe base portion 80 is reduced, the rigidity of the base portion 80 ismaintained.

As shown in FIG. 5, the tip portion of the probe 160 includes arectangular portion 162 whose shape is the same as that of the wiringopening 14. The distance from the tip end of the probe 160 torectangular portion 162 is substantially the same as that from thewriting terminal port 150 to the wiring opening 14. With theconfiguration mentioned above, five terminal pins 161 and the writingterminal port 150 are aligned and electrically connected by insertingthe rectangular portion 162 of the probe 160 into the wiring opening 14.Alternatively, the terminal pins 161 and the wiring opening 14 maybealigned by just aligning edge or side portions of wiring opening 14 andthe rectangular portion 162.

Second Preferred Embodiment

Referring to FIGS. 4, 12, 15, and 16, the second preferred embodiment ofthe present invention will be described below. In this preferredembodiment of the present invention, the writing opening and/or wiringopening is not provided on the base portion, and the writing terminalportion is provided on an armature-side of the circuit board. The restof the configuration of the axial fan 1 is similar to that explained inthe first preferred embodiment, therefore detailed explanation will beomitted.

The shaft 5 a of the axial fan 1 is retained by attaching a wire ring,such as C rings, to a circular groove arranged on the tip of the shaft 5a. In other words, the shaft 5 a is released by detaching the wire ring.Therefore, an impeller assembly 40 (rotor portion) of the axial fan 1,defined by the impeller 4, the magnet 68, the yoke 65, and the shaft 5a, is easily detached from the stationary portion as shown in FIG. 12.Moreover, the impeller assembly 40 is easily secured to the stationaryportion by attaching the wire ring.

The procedure to write data in the embedded memory of the IC 12installed onto the axial fan 1 is described below. First, power supplyfor the axial fan 1 is shut off. Second, in the state the impellerassembly 40 is detached from the axial fan 1, the probe 160 of thecontrol cable of the external memory writer is inserted into the housing2 from one end side of the housing (the armature 10 side relative to thecircuit board 110), and then the tip end of the probe 160 is connectedto the write terminal port 150. Third, by activating the externalprogram writer, data stored in the embedded memory of the IC 12 may bemodified. After writing data to the embedded memory, access to thememory is shut off to prevent the data stored in the memory from leakingout or being altered.

In this preferred embodiment of the present invention, the circuit board110 is substantially axially covered by the base portion 80. By virtueof the configuration mentioned above, the probe 160 cannot be connectedto the circuit board 110 from the base side as long as a through hole ora notch portion is not provided on the cover portion 80. Therefore, adata-writing step is performed in the state that the impeller assembly40 is not attached to the stationary portion.

As another example, as shown in FIG. 15, a modification of the secondpreferred embodiment of the present invention is preferably applied to abrushless DC motor in which an insulating material 200 is arrangedbetween the circuit board 110 and the base portion 80. The brushless DCmotor having a housing 2 defined by a conductive material (such as diecast aluminum) includes the insulating material 200 between the circuitboard 110 and the base portion 80. Therefore, the probe 160 is notconnected to the circuit board from the base portion 80 side of thebrushless DC motor.

The axial fan 1 may be used under high-temperature and high-humidityconditions. In that case, as shown in FIG. 16, moisture proofing isapplied to one surface of the circuit board 110 of the axial fan 1, onwhich electric components including IC 12 are mounted, by coating thesurface 111 with a moisture proofing agent 201, such as a polyolefin,acryl, polyurethane, or silicon. Therefore, the one surface 111 (thebase portion 80 side) of the circuit board is covered with the moistureproofing agent 201 and the probe 160 is not connected to the circuitboard from the base portion 80 side.

Moreover, in the state that the impeller assembly 40 is not attached tothe stationary portion, the armature 10 does not protrude axially abovethe writing terminal port 150. Therefore, the visibility of writingterminal portion 150 in the axial direction is properly maintained, andthe data-writing step may be facilitated. In addition, because thevisibility of the writing terminal port 150 in the axial direction isproperly maintained, the probe 160 may contact the writing terminal port150 by a linear action. Therefore, when the probe 160 is attached toautomated machinery for assembling the axial fan according to thepreferred embodiments of the present invention, it is possible tosimplify the action of the automated machinery.

Third Preferred Embodiment

Referring to FIG. 11, the third preferred embodiment of the presentinvention will be described below. In this preferred embodiment of thepresent invention, the axial fan 1 includes a circuit board 115 insteadof circuit board 110 shown in FIG. 3. The circuit board 115 has aprotruding portion 156 which radially protrudes from the outercircumferential edge of the base portion 80. Moreover, the circuit board115 includes terminal pins 155, defining the writing terminal port 150,on the protruding portion 156. In this configuration, a portion of theairflow passing through the hollow cylindrical body 3 is fed toward thecenter of the circuit board 115 to cool the electric components. Inaddition, a thermal sensor may be arranged on the protruding portion156. By virtue of this configuration, visibility of the writing terminalport is further improved so that the connection between the writingterminal port 150 and the probe 160 is easily established.

Fourth Preferred Embodiment

Referring to FIG. 17, the fourth preferred embodiment of the presentinvention will be described below. In this preferred embodiment of thepresent invention, as shown in FIG. 17, the control cable is connectedto the circuit board 110 or 115 via an auxiliary cable 19 so that theconnection between the control cable and the circuit board isestablished without directly contacting each other (cable M is not shownin FIG. 17). In other words, one end of the auxiliary cable 19 isconnected to the terminal pins of the writing terminal port 150 arrangedon the circuit board 110 or 115, and another end of the auxiliary cable19 is connected to an external circuit board 20 a arranged outside ofthe housing 2. The external circuit board 20 a includes an externalwriting terminal port defined by terminal pins 158, having a similarconfiguration and functions as the writing terminal port 150.

The external circuit board 20 a may be fixed to a casing providedseparately from the housing 2 so that the external circuit board 20 a isattached to the housing 2 in a detachable manner. Alternatively, theexternal circuit board 20 a may be attached to a device to which theaxial fan 1 is to be installed. In addition, the casing may be used as asupporting member of the external circuit board 20 a while writing datato the embedded memory of the micro computer. Alternatively, theexternal circuit board 20 a may be directly attached to the exterior ofthe housing 2.

The auxiliary cable 19 may be also used as the cable M. In this case, aDIP switch may be provided on the axial fan 1. The DIP switch switchesthe connection of the cable M to the writing terminal port when thepower supply is shut off. By virtue of this configuration, the number ofcables outgoing from the axial fan 1 is reduced.

Writing Terminal Port

Upon axially pressing the probe 160 to the writing terminal port 150,the circuit board 110 axially supports the writing terminal port 150whereby the probe 160 and the writing terminal port 150 are securelyconnected. In case terminal pins 161 of the probe 16 are damaged by thepressure upon pressing the probe 160 to the writing terminal port 150,each of terminal pins 161 may be constructed to have elasticity. Forexample, as shown in FIG. 6, elastic terminal pins 152 may be providedon the writing terminal port 150.

In case the writing terminal port 150 and the probe 160 are not alignedproperly, a data-writing error may occur. Therefore, to write dataproperly, the writing terminal port 150 and the probe 160 need to beproperly aligned. For example, as shown in FIG. 7, connectors c1 and c2,arranged on the tip ends of the probe 160 and the writing terminal port150 respectively, may be connected to each other to align the probe 160and the writing terminal port 150. Alternatively, as shown in FIG. 8, aconnector c3 arranged on the writing terminal port 150 and the connectorc1 of the probe 160 may be connected to each other. Alternatively, asshown in FIG. 9, a through hole c4 may be provided on the circuit board110 and a conductive portion may be provided on the inner peripheralsurface of the circuit board 110 defining the through hole c4. Then theconnector c1′ may be inserted into the through hole C4. Alternatively,as shown in FIG. 10, a notch portion c5 provided on the circuit board110 and a convex portion 163 provided on the rectangular portion 162 ofthe probe 160 may contact with each other to align the writing terminalport 150 and the probe 160. While examples of aligning the writingterminal port 150 and the probe 160 have been described in theforegoing, it is not limited to the examples described above, in thatvarious modifications are possible.

According to the preferred embodiments of the present invention, thedata stored in the embedded memory of the IC may be easily modifiedafter the IC is installed onto the axial fan. Therefore, the settings ordesign of the axial fan 1 may be modified without replacing the alreadyinstalled IC 12 and/or the circuit board 110. In other words, the datastored on the IC installed to the axial fan 1 can be modified in anefficient manner without high increased costs and/or time consumingprocedures. Moreover, the data may be modified any number of timesbecause the flash memory is used as the embedded memory of the IC.

Additionally, the axial fan may be completely assembled or partiallyassembled. The partially assembled axial fan includes, for example, thecircuit board 110 on which the IC 12 is mounted; the assembly defined bythe housing 2, the armature 10, the pair of bearings, and the circuitboard 110; and the assembly defined by the armature 10 and the circuitboard 110.

Manufacturing Method of the Axial Fan

Next, a manufacturing method of the axial fan is explained.

In the case that the data is stored in the embedded memory of the IC 12of the axial fan 1 just before the shipment thereof, the data ismodified by the method as shown in FIG. 13.

First, the impeller assembly 40 is detached from the stationary portion.By detaching a C-ring arranged on the tip end portion of the shaft 5 a,the shaft 5 a becomes axially movable, whereby the impeller assembly 40is detached from the stationary portion. By detaching the impellerassembly 40, the writing terminal port 150 arranged on the circuit board110 is exposed. Subsequently, the probe 160 is electrically connected tothe writing terminal port 150 and the data stored in the memory ismodified. Then, the impeller assembly 40 is attached to the stationaryportion and the rotation thereof is inspected in relation to the currentwaveform, the rotation speed, and so on. If an error is found in theaxial fan, the impeller assembly 40 is detached and the data istransferred to the memory again.

Referring to FIG. 14, the manufacturing method of the axial fan 1 isdescribed in detail with a focus on the data-writing step. In thispreferred embodiment, the predetermined data relating to the rotationcontrol has been already written in the embedded memory of the IC 12.Before writing data in the memory, the IC 12 is mounted to the circuitboard 110. Therefore, the IC 12 with predetermined data mounted on thecircuit board 110 is fed to the manufacturing process of the axial fan1.

First, the circuit board 110 is electrically connected with the coilformed on the armature 10. Second, the circuit board 110 and thearmature 10 electrically connected to each other are attached to thebase portion 80 of the housing 2. The armature 10 is bonded to the outercircumferential surface of the bearing housing 85 arranged at the middleportion of the base portion 80 with, for example, adhesive. Therefore,the armature 10 and the circuit board 110 are not easily detached oncethe adhesive is hardened.

Third, the pair of ball bearings is fixed to the inside of the bearinghousing 85, and the shaft 5 a and a portion of the impeller assembly 40is inserted into the pair of ball bearings such that the shaft 5 a isrotatably supported via the bearings. Fourth, power is provided to thecircuit board 10, and the rotation of the impeller assembly 40 isinspected. In this step, various factors, such as the rotation speed,waveform of the electric current flowing through the motor, the rotationspeed of the impeller assembly 40 upon sending the control signal to themotor, etc. are inspected. Predetermined standards are given to suchfactors, and the motors which do not meet the standards are recognizedas defective motors. Causes of the defects are, for example, writingerror on the IC 12, writing false data on the IC 12, defects of the IC12, and defects of the electric components other than IC 12. When adefective motor is found, the impeller assembly 40 of the defectivemotor is detached and data is written to the IC 12 again.

While preferred embodiments of the present invention have been describedin the foregoing, the present invention is not limited to the preferredembodiments detailed above, in that various modifications are possible.

For example, the circuit board 110 or 115 maybe any suitable circuitboard, such as a flexible circuit board and a rigid circuit board madeof metal, glass epoxy board, or paper impregnated phenol resin sheet.

Additionally, the writing terminal port may be arranged on an endsurface of the circuit board, and the control cable from the externalmemory writer may be connected to the writing terminal port from theradial direction.

Additionally, the connection between the writing terminal port and theexternal memory writer may be established in a wireless manner. Forexample, a wireless signal receiver, such as an infra-red signalreceiver, may be connected to the writing terminal port, and a wirelesssignal transmitter may be connected to the external memory writer.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A brushless DC motor comprising: a rotor portion rotatable about a center axis and including a magnet; a stationary portion including an armature facing the magnet, the armature defined by a wire wound around a stator core; a bearing rotatably supporting the rotor portion relative to the stationary portion; a base portion; a circuit board connected to and facing the armature; a rotation control portion provided on the circuit board and including a non-volatile rewritable memory arranged to control the rotation of the rotor portion based on data stored in the non-volatile rewritable memory; a driving circuit provided on the circuit board and arranged to provide driving current controlled by the rotation-control portion; and a writing terminal port provided on the circuit board and arranged to be detachably connected to an external memory writer; wherein the circuit board is axially arranged between the armature and the base portion; and the writing terminal port is arranged on a side of the circuit board facing the base portion, the base portion includes a writing opening, and the writing terminal port is arranged to be detachably connected to the external memory writer via the writing opening.
 2. The brushless DC motor as set forth in claim 1, further comprising: an impeller arranged on the rotor portion to generate an air flow; a bearing housing having a hollow cylindrical shape, an inside of which supports the bearing and an outside of which supports the armature; the base portion extending radially outwardly from the bearing housing; a housing surrounding the impeller and defining a passage for the air flow; and a supporting arm supporting the base portion relative to the housing by connecting the housing and the base portion.
 3. The brushless DC motor as set forth in claim 2, wherein the circuit board includes a protruding portion which radially protrudes from the base portion, and the writing terminal port is arranged on the protruding portion.
 4. The brushless DC motor as set forth in claim 2, wherein the external memory writer and the writing terminal port are detachably connected by a control cable, and the writing terminal port is arranged to be detachably connected to a tip end portion of the control cable in the radial direction of the circuit board.
 5. The brushless DC motor as set forth in claim 4, wherein the writing terminal port is arranged on an end surface of the circuit board.
 6. The brushless DC motor as set forth in claim 2, further comprising one end of an auxiliary cable connected to the writing terminal port and another end of the auxiliary cable connected to an external writing terminal port, and the external writing terminal port is arranged to be detachably connected to a control cable.
 7. The brushless DC motor as set forth in claim 1, wherein the circuit board includes an external connection port to which a cable from at least one of an external power source and an external control circuit is connected, and the cable is led outside of the brushless DC motor through the writing opening.
 8. The brushless DC motor as set forth in claim 2, wherein the external memory writer and the writing terminal port are arranged to be detachably connected by a control cable, and at least a portion of the base portion defining the writing opening is arranged to align a tip end portion of the control cable and the writing terminal port.
 9. The brushless DC motor as set forth in claim 1, wherein the external memory writer and the writing terminal port are arranged to be detachably connected by a control cable, and at least a portion of the base portion defining the writing opening is arranged to align a tip end portion of the control cable and the writing terminal port.
 10. The brushless DC motor as set forth in claim 1, wherein the circuit board includes a connector on the writing terminal port, and a control cable from the external memory writer is detachably connected thereto.
 11. The brushless DC motor as set forth in claim 1, wherein the circuit board includes a hole or a notch portion, and the hole or notch portion is arranged to align the writing terminal port with a tip end portion of a control cable connected to the external memory writer.
 12. The brushless DC motor as set forth in claim 1, wherein a wireless signal receiver is attached to the writing terminal port and the external memory writer is to be connected to the circuit board in a wireless manner. 